Integration of Inferior Vena Cava Measurements into Routine Functional Echocardiography in Preterm Neonates: Are We There Yet?

Integration of Inferior Vena Cava Measurements into Routine Functional Echocardiography in Preterm Neonates: Are We There Yet? | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Integration of Inferior Vena Cava Measurements into Routine Functional Echocardiography in Preterm Neonates: Are We There Yet? Irem Unal, Ebru Yalin Imamoglu, Sibel Hatice Ozumut, Fahri Ovali This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5342801/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract Objective To evaluate baseline inferior vena cava measurements and investigate the clinical factors that may affect inferior vena cava diameters and hemodynamic changes during the first week of life in preterm neonates. Study Design: This prospective observational study included a consecutive cohort of 30 preterm neonates born at < 34 weeks gestation. Echocardiographic parameters and inferior vena cava diameters were measured on the postnatal 1st, 3rd, and 7th days, and inferior vena cava indices were calculated. We then compared echocardiographic and inferior vena cava parameters in different types of respiratory support. Result Baseline data of the inferior vena cava parameters were reported. The median values of the inferior vena cava collapsibility, distensibility, and respiratory variation indices did not change at different respiratory levels. Conclusion Inferior vena cava collapsibility, distensibility, and respiratory variation indices remained stable with varying levels of respiratory support. These indices might be integrated into routine hemodynamic assessment to determine preload and intravascular volume status. Health sciences/Medical research Health sciences/Medical research/Outcomes research Inferior vena cava echocardiography hemodynamics preterm neonates Figures Figure 1 Figure 2 INTRODUCTION Functional echocardiography has become crucial for assessing cardiac function and hemodynamic status in neonatal intensive care units (NICUs) ( 1 ). Among various echocardiographic parameters, inferior vena cava (IVC) measurements may provide valuable insights in the assessment of preload and intravascular volume status ( 2 – 4 ). The IVC, a structurally thin-walled and highly compliant vessel, varies in size and dynamics with changes in respiration and intravascular volume ( 5 ). This causes pulsatility during different respiratory and cardiac cycles. While these variations are primarily driven by the physiological effects of respiration, several other factors can influence IVC diameters, including intravascular volume, increased mean airway pressure, elevated pulmonary vascular resistance, heart failure, cardiac tamponade, or pneumothorax ( 6 ). Evaluation of the IVC parameters can help clinicians assess hemodynamic status and guide fluid management ( 3 ). McNamara et al. reported that IVC parameters could be used for assessing volume changes; however, these parameters are not well established in neonates, particularly those with invasive ventilation ( 6 ). Until now, there have been a limited number of studies in the literature that integrate IVC parameters into hemodynamic assessments by functional echocardiography in neonates ( 7 – 10 ). The current international guidelines support the use of the IVC collapsibility index (CI) for the assessment of cardiac preload and intravascular status; however, there are no validated normative data available in the neonatal population ( 4 , 11 ). Therefore, in this study we report baseline IVC measurements and investigate the clinical factors that may affect IVC diameters, as well as the hemodynamic changes during the first week of life in preterm neonates. METHODS Study Design and Setting This prospective observational study was performed in the NICU at Istanbul Medeniyet University between February 2023 and January 2024. The Institutional Review Board approved the study, and informed consent was obtained from parents before inclusion. Participants A consecutive cohort of 30 preterm neonates who were born at < 34 weeks gestation, were admitted to the NICU, and survived during the first week of life were included in the study. Preterm neonates with conditions that affect intravascular status, like placental abruption, vasa previa, fetomaternal hemorrhage, and fetoplacental hemorrhage, were excluded. Cases of perinatal asphyxia, pericardial effusion, and pneumopericardium, which can cause cardiac dysfunction, and cases with pneumothorax were not included. Also, those with congenital defects, with chromosomal or other genetic abnormalities, or whose IVC could not be visualized with echocardiography were excluded from the study. Data Collection and Follow-up All preterm neonates were followed for the first week of their lives. Demographic, clinical, and maternal data, including gestational age, birth weight, gender, mode of delivery, maternal diseases, antenatal steroid administration, cord management, presence of respiratory distress syndrome or transient tachypnea of the newborn, and surfactant administration were recorded. Preterm neonates were evaluated on the postnatal 1st, 3rd, and 7th days. Parameters including weight loss, total fluid intake, hemoglobin level, type of respiratory support, mean airway pressure, presence of intraventricular hemorrhage, sepsis, hemodynamically significant patent ductus arteriosus (hsPDA), systemic hypotension, use of inotropes, pulmonary hypertension (PHT), and inhaled nitric oxide (iNO) treatment were noted. Blood pressure was assessed by measuring systolic, diastolic, and mean arterial pressures and analyzing the trends of all measurements using a noninvasively oscillometric method (HWATIME XM750; Shenzhen Hwatime Biological Medical Electronic, Shenzhen, China). Hypotension was diagnosed if at least two values were below 2 standard deviation (SD) values for the gestational and postnatal age or if there was a trend of ≥ 20% decrease in blood pressure parameters for more than 30 minutes ( 12 , 13 ). Lung Ultrasonography All patients underwent lung ultrasound (LUS) to evaluate the presence of any lung pathology (respiratory distress syndrome, transient tachypnea of the newborn, pulmonary hemorrhage, congenital pneumonia, or pneumothorax), fluid overload, or lung aeration. Surfactant treatment was performed at the discretion of the attending neonatologist, and LUS was performed independently from the surfactant treatment. Lung ultrasonography was performed with a Vivid S60N scanner (General Electric Medical Systems, Milwaukee, WI, USA) using an 11 L-D linear probe. Each lung was divided into three zones (upper anterior, lower anterior, and lateral) and examined with longitudinal scans. For each lung zone, a 0- to 3-point score was given (total score ranging from 0 to 18). The LUS score was assigned as follows: score 0 indicates A-pattern (defined by the presence of only A-lines); score 1, B-pattern (defined as the presence of ≥ 3 well-spaced B-lines); score 2, severe B-pattern (defined as the presence of crowded and coalescent B-lines with or without consolidations limited to the subpleural space); and score 3, extended consolidations ( 14 ). The diameters and dynamics of the IVC, a highly compliant vessel, can increase with intravascular volume overload. Therefore, with LUS, we assessed the presence of B-line burden, reflecting the degree of lung edema, which could be seen in cases of volume overload ( 15 ). The A-line pattern is observed in both a normal and hyperinflated lung. In ventilated patients, hyperinflated lungs increase right atrial pressure, resulting in IVC distension ( 2 ). Since LUS has some limitations for monitoring hyperinflation due to excessive mechanical ventilation, we planned to evaluate routine chest X-ray radiographs of the patients. Lung aeration was considered adequate when the right hemidiaphragm was at the level of the 8th rib posteriorly. Patients with flattening of diaphragms and lung expansion > 8th posterior ribs were diagnosed with hyperinflation ( 16 ). Functional Echocardiography Echocardiographic parameters were evaluated with a GE Vivid S60N scanner (Boston, MA, USA) using a 12S phased-array sector probe. To eliminate inter-observer variability, all measurements were performed by the same experienced neonatologist (I.U.). All neonates were scanned in a resting state in the supine position. To provide a comprehensive evaluation of the cardiac functions, we assessed preload, left ventricular output (LVO), right ventricular output (RVO), tricuspid annular plane systolic excursion (TAPSE), and right ventricular (RV) fractional area change (FAC). Patients were screened for PHT on the 1st, 3rd, and 7th days and for hsPDA on the 3rd and 7th days, based on criteria outlined in previously referenced sources ( 17 – 19 ). In the apical four-chamber view of the heart, we assessed left ventricular filling. We estimated whether there is a kissing sign by eye-balling the difference between end-systolic and end-diastolic volumes of the left ventricle ( 20 ). Then, the right upper pulmonary vein (RUPV) was visualized along the interatrial septum in the upper part of the left atrium using color flow Doppler to assess preload. The orifice of the RUPV was imaged at the bottom of the red color Doppler flow, and the pulsed Doppler sample volume was placed into the vessel. RUPV peak systolic velocity (RPUV PV) (m/s) was measured, considering a normal range of 0.2–0.5 m/s ( 21 – 23 ). Tricuspid annular plane systolic excursion and RV FAC were also evaluated to detect the RV function in this apical four-chamber view. Tricuspid annular plane systolic excursion was determined by placing the M-mode cursor through the lateral tricuspid annulus and measuring the extent of longitudinal annular motion during peak systole ( 4 ). We used two-dimensional images from the apical four-chamber view to calculate RV FAC. Offline analysis involved identifying the RV cavity end-diastolic area (RVEDA) and end-systolic area (RVESA) and manually tracing the cavity area. Right ventricle FAC was calculated using the following formula: [RVEDA - RVESA] / RVEDA × 100 ( 24 ). In the apical five-chamber view, we evaluated LVO to determine left ventricular function. We placed the pulsed wave Doppler above the aortic valve in the apical five-chamber view for velocity time integral (VTI), and we measured the size of the aortic valve annulus at end-systole from the parasternal long-axis view. Left ventricular output was then calculated using this formula: [3.14 × (diameter (cm) / 2)² × VTI × HR] / weight (kg) ( 1 ). In the parasternal short-axis view at the level of the pulmonary valve, we evaluated the RV function by measuring RV outflow tract diameter at end-systole, and RVO VTI was obtained by tracing the pulsed wave Doppler waveform at the same level. Right ventricular output was calculated using the same formula as LVO ( 1 ). Inferior Vena Cava Measurements with Echocardiography All IVC measurements were performed in the supine position. The ultrasound probe was placed in the substernal area with the marker pointing toward the head of the neonate. The probe was tilted rightward from the midline until it captured the longitudinal view of the IVC as it merged into the right atrium. Since the probe movement off-midline might result in measurements of a false diameter smaller than the true IVC diameter, we tried to obtain a true midline image of the IVC. The M-mode cursor was placed perpendicular to the vessel. The image was frozen, and IVC diameters were measured 1 cm caudal to the junction where the hepatic vein drains into the IVC. Then, maximum and minimum diameters of the IVC (IVC max and IVC min ) were obtained in millimeters using calipers ( 2 , 11 ) (Fig. 1 ). The IVC collapsibility index (CI), distensibility index (DI), and respiratory variation index (RVI) were calculated with the following formulas: Collapsibility Index = [(IVC max - IVC min ) / IVC max ] × 100, Distensibility Index = [(IVC max - IVC min ) / IVC min ] × 100, Respiratory Variation Index = [(IVC max - IVC min ) / ((IVC max + IVC min ) / 2)] × 100. After viewing the IVC, the ultrasound probe was tilted to the left from the midline in the same echo window. The diameter of the abdominal aorta was assessed at 1 cm above the celiac trunk's origin in the longitudinal plane in B-mode ( 1 , 11 ) (Fig. 2). Then, the IVC max / abdominal aorta (IVC max /Ao) and IVC min / abdominal aorta (IVC min /Ao) ratios were calculated. All the IVC and aorta diameters were measured from the inner wall to the inner wall. Statistical Analysis Statistical analyses were performed using the SPSS software version 26 (SPSS Inc., Chicago, IL, USA). The variables were investigated using visual (histograms, probability plots) and analytical methods (Kolmogorov-Smirnov test, Shapiro-Wilk test) to determine whether they were normally distributed. Descriptive analyses were presented using means and SD as the normally distributed variables. Median and interquartile range (25th and 75th percentile of distribution) were used for non-normally distributed variables. Nonparametric variables were compared using the Mann-Whitney U test, and categorical variables were compared using the chi-square test or Fisher’s exact test (when chi-square test assumptions did not hold due to low expected cell counts), where appropriate. The Friedman test was conducted on ordinal or continuous variables in the case of violations of parametric test assumptions on the 1st, 3rd, and 7th days. Echocardiographic measurements and IVC parameters were compared between different respiratory support levels. Since only one patient had no respiratory support on the 1st day, comparisons were made between noninvasive support and mechanical ventilation. Nonparametric variables were compared using the Mann-Whitney U test. Student’s t-test and Welch’s test were used for normally distributed variables. On the 3rd and 7th day, nonparametric variables were compared with the Kruskal-Wallis test. One-way ANOVA and Welch’s ANOVA test were used for normally distributed variables. Bonferroni correction was applied to all values. Statistically significant and nonsignificant values were reported with their corresponding 95% confidence interval values. A p-value of less than 0.05 was considered to show a statistically significant result. Intra-observer variability was assessed in a randomly selected sample of 20 neonates. The same investigator, blinded to the initial results, repeated the measurements. The coefficient of variation was calculated to quantify the intra-observer variability. RESULTS Demographic characteristics of the study group are presented in Table 1 . The clinical parameters on the postnatal 1st, 3rd, and 7th days are presented in Table 2 . Table 3 summarizes echocardiographic measurements and IVC parameters on the postnatal 1st, 3rd, and 7th days. There was a statistically significant increase in the median values of LVO, RVO, and TAPSE during the first postnatal week. Other echocardiographic parameters, including median RUPV PV and FAC values, were similar during the first postnatal week. When IVC parameters were examined, median IVC max , IVC CI, IVC DI, and IVC RVI values were found to be ​​higher on the 3rd day and at their lowest level on the 7th day. However, median IVC max /Ao values ​​were at their lowest levels on the 1st day, higher on the 3rd day, and then lower again. The other IVC parameters did not change significantly throughout the first week. The time required to perform a bedside evaluation of the IVC was approximately 1–2 minutes. The intra-observer error was minimal (2%), and no significant difference was observed between the consecutive measurements. Table 1. Demographic data of the study group n:30 Gestational age, median (IQR) Gestational age, n (%) 23-27 wk 28-31 wk 32-34 wk 30 [29-32] 9 (30) 17 (56.7) 4 (13.3) Birth Weight, g, median (IQR) Birth Weight, n (%) 2500 g 1347 [974-1587] 10 (33.3) 11 (36.7) 8 (26.7) 1 (3.3) Female, n (%) Male, n (%) 12 (40) 18 (60) C-section, n (%) 24 (80) Antenatal Steroids, n (%) None Half dose Full dose 1 (3.3) 8 (26.7) 21 (70) Maternal Diseases, n (%) None PPROM GDM Preeclampsia 17 (56.7) 7 (23.3) 3 (10) 3 (10) Cord clamping method, n (%) ICC DCC Milking ICR 26 (86.7) 1 (3.3) 1 (3.3) 2 (6.7) RDS, n (%) TTN, n (%) 18 (60) 12 (40) Surfactant treatment, n (%) none single dose two doses three doses 12 (40) 13 (43.3) 4 (13.3) 1 (3.3) IQR: interquartile range, PPROM: preterm premature rupture of membranes, GDM: gestational diabetes mellitus, ICC: immediate cord clamping, DCC: delayed cord clamping, ICR: intact cord resuscitation, RDS: respiratory distress syndrome, TTN: transient tachypnea of the newborn. Table 2 Comparison of clinical parameters on the 1st, 3rd, and 7th postnatal days 1st Day 3rd Day 7th Day p Weight Change (%), median [IQR] 0 [-4.95, 0] -8.1 [-12.2, -1] -4.24 [-10.53, 2.18] < 0.001* Total Fluid Intake (ml/kg/day), median [IQR] 70 [70–80] 120 [120–140] 150 [140–160] < 0.001* Hb, median [IQR] 17.9 [15.9–19.5] 16.2 [14.7–19.4] 15.8 [14-17.3] < 0.001* MAP, median [IQR] 8.8 [7-10.5] 7 [6-8.5] 6.5 [0-9.5] 0.024* IVH, n (%) Stage 1 Stage 2 Stage 3 PVHI 2 (6.7) 0 (0) 0 (0) 0 (0) 2 (6.7) 5 (16.7) 0 (0) 1 (3.3) 0 (0) 4 (13.3) 7 (23.3) 1 (3.3) 2 (6.7) 0 (0) 4 (13.3) 0.2 hsPDA, n (%) - 5 (16.7) 4 (13.3) 0.484 Sepsis, n (%) 4 (13.3) 9 ( 30 ) 11 (36.7) 0.109 Hypotension, n (%) 1 (3.3) 2 (6.7) 1 (3.3) 0.771 LUS score (B-line burden), median (IQR) 5 [2.2-6] 3 [2-6.7] 3 [0.2-6] 0.037* IQR: interquartile range, nCPAP: nasal continuous positive airway pressure, NIPPV: noninvasive positive pressure ventilation, SIPPV: synchronized intermittent positive pressure ventilation, HFOV: high-frequency oscillatory ventilation, MAP: mean airway pressure, IVH: intraventricular hemorrhage, PVHI: periventricular hemorrhagic infarct, hsPDA: hemodynamically significant patent ductus arteriosus, PHT: pulmonary hypertension, LUS: lung ultrasound score. P values marked with asterisk (*) were calculated with the Friedman test. Other p values were calculated with the chi-square test. Statistically significant p values were marked as bold. Table 3 Changes in echocardiographic measurements and inferior vena cava parameters on the postnatal 1st, 3rd, and 7th days Variable, median (IQR) 1st Day 3rd Day 7th Day p Echocardiographic Measurements RUPV PV (m/sec) 0.35 [0.31–0.43] 0.40 [0.35–0.47] 0.41 [0.33–0.44] 0.335 LVO (ml/kg/min) 174 [136–206] 196 [162–263] 210 [188–256] < 0.001 RVO (ml/kg/min) 318 [237–369] 399 [354–485] 455 [344–541] < 0.001 TAPSE (cm) 0.60 [0.50–0.70] 0.70 [0.60–0.87] 0.80 [0.61–0.90] 0.026 FAC (%) 21 [15–25] 26 [17–30] 27 [23–30] 0.233 IVC parameters IVC max (mm) IVC min (mm) 2.77 [2.36–3.33] 2.08 [1.80–2.45] 3.09 [2.59–3.47] 2.33 [1.65–2.60] 2.63 [2.32–3.27] 2.03 [1.74–2.48] 0.048 0.662 IVC CI (%) 22.24 [17.39–27.94] 26.20 [18.31–37.65] 21.45 [16.8–28.9] 0.034 IVC DI (%) 28.61 [21.06–38.77] 35.51 [22.42–60.45] 27.33 [20.21–40.65] 0.034 IVC RVI (%) 25.02 [19.05–32.48] 30.15 [20.16–46.4] 24.03 [18.34–33.79] 0.034 IVC max / Ao 0.62 [0.58–0.70] 0.68 [0.62–0.77] 0.64 [0.59–0.76] 0.003 IVC min / Ao 0.47 [0.40–0.53] 0.49 [0.40–0.59] 0.48 [0.40–0.59] 0.771 RUPV PV: right upper pulmonary vein peak velocity, LVO: left ventricular output, RVO: right ventricular output, TAPSE: tricuspid annular plane systolic excursion, FAC: fractional area change, IVC max : maximum diameter of inferior vena cava, IVC min : minimum diameter of inferior vena cava, IVC CI: inferior vena cava collapsibility index, IVC DI: inferior vena cava distensibility index, IVC RVI: inferior vena cava respiratory variation index, IVC max / Ao: ratio of maximum diameter of the inferior vena cava to abdominal aorta, IVC min / Ao: ratio of minimum diameter of inferior vena cava to abdominal aorta. P values were calculated using the Friedman test. Statistically significant p values were marked as bold. During the first week, we compared echocardiographic measurements and IVC parameters in different types of respiratory support (spontaneous breathing, noninvasive, and invasive mechanical ventilation [MV]). On the 1st postnatal day, echocardiographic and IVC parameters were similar in different types of respiratory support. On the 3rd postnatal day, an increase in the median values of IVC max and IVC max /Ao was observed as respiratory support was escalated (Table 4 ). Post hoc analyses revealed a significant increase in IVC max between the noninvasive and MV groups (p = 0.042) and in IVC max /Ao between the spontaneous and MV groups (p = 0.036). On the 7th postnatal day, the median values of IVC min , IVC max /Ao, and IVC min /Ao were found to increase with higher levels of respiratory support. Post hoc analysis revealed a significant difference in the median values of IVC min , IVC max /Ao, and IVC min /Ao between the spontaneous and MV groups (p = 0.036, p = 0.024, and p = 0.042, respectively). However, the median values of IVC CI, DI, and RVI did not change during the first week in different respiratory support levels. Table 4. Echocardiographic measurements and IVC parameters in different ventilation modes Spontaneous Breathing Noninvasive Respiratory Support Mechanical Ventilation p Cases, n (%) Day 1 Day 3 Day 7 1 (3.3) 4 (13.3) 10 (33.3) 21 (70) 20 (66.6) 13 (43.3) 8 (26.6) 6 (20) 7 (23.3) RUPV PV (m/sec) Day 1, median [IQR] Day 3, mean±SD Day 7, mean±SD - 0.36 ± 0.01 0.40 ± 0.07 0.38 [0.32-0.47] 0.42 ± 0.1 0.43 ± 0.09 0.32 [0.29-0.35] 0.46 ± 0.09 0.33 ± 0.09 0.744** 0.245 0.052 LVO (ml/kg/min) Day 1, mean±SD Day 3, mean±SD Day 7, mean±SD - 156 ± 42 199 ± 53 176 ± 54 194 ± 56 228 ± 49 184 ± 99 369 ± 108 278 ± 119 1*** 0.072 **** 1**** RVO (ml/kg/min) Day 1, mean±SD Day 3, mean±SD Day 7, mean±SD - 306 ± 131 360 ± 98 317 ± 124 411 ± 90 494 ± 134 282 ± 76 471 ± 93 479 ± 183 1* 0.258 0.408 TAPSE (cm) Day 1, median [IQR] Day 3, mean±SD Day 7, mean±SD - 0.75 ± 0.19 0.86 ± 0.14 0.7 [0.6-0.7] 0.72 ± 0.14 0.70 ± 0.18 0.5 [0.5-0.5] 0.70 ± 0.14 0.65 ± 0.19 0.06** 1 0.270 FAC (%) Day 1, mean±SD Day 3, mean±SD Day 7, mean±SD - 26 ± 6 23 ± 9 20 ± 6 22 ± 9 28 ± 9 24 ± 1 30 ± 11 23 ± 9 1* 1 1 IVC max (mm) Day 1, mean±SD Day 3, mean±SD Day 7, mean±SD - 2.73 ± 0.54 2.50 ± 0.52 2.93 ± 0.61 2.95 ± 0.46 2.72 ± 0.40 2.66 ± 0.70 3.77 ± 0.75 3.21 ± 0.61 1* 0.030 0.144 IVC min (mm) Day 1, mean±SD Day 3, mean±SD Day 7, mean±SD - 2.13 ± 0.65 1.83 ± 0.32 2.23 ± 0.58 2.14 ± 0.56 2.11 ± 0.44 2.18 ± 0.72 2.45 ± 0.68 2.60 ± 0.55 1* 1 0.036 IVC CI (%) Day 1, mean±SD Day 3, mean±SD Day 7, mean±SD - 22.76 ± 11.95 25.34 ± 9.82 24.16 ± 8.95 28.02 ± 12.95 29.31 ± 13.63 19.01 ± 6.51 34.47 ± 14.21 18.59 ± 12.80 0.91* 1 1 IVC DI (%) Day 1, mean±SD Day 3, mean±SD Day 7, mean±SD - 31.92 ± 22.11 36.51 ± 17.12 33.76 ± 17.12 44.42 ± 33.38 30.85 ± 14.45 24.17 ± 9.83 60.02 ± 41.53 24.85 ± 16.55 0.894** 1 1 IVC RVI (%) Day 1, mean±SD Day 3, mean±SD Day 7, mean±SD - 26.43 ± 15.39 30.10 ± 11.81 28.05 ± 11.94 33.93 ± 18.92 26.11 ± 10.67 21.26 ± 7.89 43.23 ± 22.15 21.33 ± 12.25 0.900** 1 1 IVC max / Ao Day 1, mean ± SD Day 3, mean ± SD Day 7, mean ± SD - 0.62 ± 0.12 0.55 ± 0.10 0.63 ± 0.09 0.69 ± 0.10 0.68 ± 0.12 0.62 ± 0.13 0.85 ± 0.14 0.78 ± 0.16 1* 0.042 0.018 IVC min / Ao Day 1, mean ± SD Day 3, mean ± SD Day 7, mean ± SD - 0.48 ± 0.15 0.40 ± 0.06 0.48 ± 0.09 0.50 ± 0.13 0.53 ± 0.12 0.50 ± 0.11 0.55 ± 0.13 0.64 ± 0.15 1* 1 0.006 RUPV PV: right upper pulmonary vein peak velocity, LVO: left ventricular output, RVO: right ventricular output, TAPSE: tricuspid annular plane systolic excursion, FAC: fractional area change, IVC max : maximum diameter of inferior vena cava, IVC min: minimum diameter of inferior vena cava, IVC CI: inferior vena cava collapsibility index, IVC DI: inferior vena cava distensibility index, IVC RVI: inferior vena cava respiratory variation index, IVC max / Ao: ratio of maximum diameter of the inferior vena cava to abdominal aorta, IVC min / Ao: ratio of minimum diameter of inferior vena cava to abdominal aorta. Bonferroni correction was applied to all P values. P values marked with corresponding symbols were calculated with (*) the Student t-test, (**) the Mann-Whitney U test, (***) the Welch’s test, and (****) the Welch ANOVA. Other p values were calculated with the One-Way ANOVA test. Statistically significant p values were marked as bold. On the 1st day, one patient had hypotension and was treated with dobutamine and adrenaline throughout the week, with terlipressin added on the 7th day. Additionally, on the 3rd day, three patients were administered dobutamine; two did not exhibit hypotension but were given inotropes based on the findings from functional echocardiography. There was no kissing sign of the left ventricle in any patient. On the 3rd postnatal day, four out of six patients receiving MV support had hsPDA. In addition, three out of these six patients received inotrope treatment. By the 7th day, no other patients were receiving inotropes, except the patient who had hypotension from the 1st day. No patients had PHT or received iNO treatment. The median LUS score reflecting B-line burden was found to be 5, 3, and 3 on the 1st, 3rd, and 7th days, respectively, which are considered low LUS scores. Volume overload was not detected in any patient. The median LUS score in patients with RDS was higher than in patients with TTN on the 1st, 3rd, and 7th days (p < 0.001 for all days). On the postnatal 3rd and 7th days, the LUS score in patients with hsPDA was statistically significantly higher than the group without hsPDA (p = 0.006 for the 3rd day, p = 0.013 for the 7th day). When routine chest X-rays were evaluated during the first week, there was no hyperinflation in any patient. DISCUSSION This study provides baseline IVC diameters and hemodynamic changes in preterm neonates during the first week of life. Also, we demonstrated that the median values of IVC indices, including CI, DI, and RVI, remained stable with varying levels of respiratory support. Fluctuations in intrathoracic pressure during the respiratory cycle significantly affect IVC diameter. During inspiration, negative intrathoracic pressure increases, reducing right atrial pressure and increasing intra-abdominal pressure, which enhances venous return and causes IVC collapse ( 2 ). Conversely, elevated intrathoracic pressure decreases venous return during expiration, leading to IVC distension. In mechanically ventilated patients, this physiological process is reversed: increased intrathoracic pressure during mechanical inspiration raises right atrial pressure, resulting in IVC distension. Abdel-Hady et al. examined IVC diameters in 25 preterm neonates during spontaneous breathing and nasal continuous positive airway pressure (nCPAP), reporting larger IVC diameters in those receiving nCPAP ( 9 ). Similarly, in our study, IVC diameters were found to be larger in neonates requiring MV. Since the physiological variations in the IVC diameters were seen during respiratory support, the use of IVC indices, including IVC CI, DI, and RVI, is preferred in clinical practice. Specifically, IVC CI is recommended for spontaneously breathing patients, while IVC DI and RVI are more appropriate for mechanically ventilated patients ( 25 – 30 ). To our knowledge, this is the first study to investigate IVC CI, DI, and RVI in preterm neonates, and also the first to compare IVC parameters based on the level of respiratory support. While the IVC diameters varied according to the levels of respiratory support, no significant change was observed in IVC CI, DI, and RVI. This finding suggests that these indices may be reliable markers for assessing cardiac preload and intravascular volume status in preterm infants, as has been demonstrated in adult and pediatric studies ( 11 , 25 – 27 , 31 – 34 ). Conlon et al. reported that cardiopulmonary interactions can significantly impact IVC-based measurements ( 3 ). They also suggested that clinicians should integrate data from all cardiac views to rule out poor function and pressure overload conditions, which may contribute to visualized IVC morphology. In our study, LVO, RVO, and TAPSE showed a significant increase in the postnatal first week, while RUPV PV and FAC values increased over time but were not statistically significant. These results suggest that cardiac function improved during the first week, possibly due to postnatal adaptation and inotropic support. Our patients’ median FAC values were lower than the normal term neonatal values. Studies on FAC in preterm infants have shown that FAC is correlated with gestational age, tends to be low in the first few days of life, and gradually increases over time ( 35 ). Similarly, the RVO values in our patients were higher than the normal term neonatal values. This observation is similar to previous studies, which have shown that RVO is typically elevated in preterm infants during the early days of life ( 36 , 37 ). Theoretically, IVC diameters could be affected by cardiac function, pulmonary vascular resistance, fluid status, and hyperinflation. Moreover, cardiac tamponade and pneumothorax may increase the IVC diameters ( 3 ). The literature lacks any IVC study that evaluates all these factors together in preterm neonates. In our study, postnatal changes in cardiac functions during the first week were consistent with gestational age, and hemodynamic parameters were within normal ranges. PHT was not present. Our patients did not have excessive weight loss or fluid overload. Also, hyperinflation was not seen in any case. Cases with cardiac tamponade and pneumothorax had already been excluded from the study. Since IVC measurements are affected by respiratory movements, there is a potential for error in diameter assessment. In an adult study evaluating IVC displacement during respiro-phasic ultrasound imaging, Blehar et al. demonstrated a significantly greater movement of the IVC in the craniocaudal direction than in the mediolateral direction, which predominantly affects IVC measurements in the transverse section ( 38 ). For this reason, we preferred to perform our measurements from the longitudinal section. To our knowledge, for the first time in the literature, Abdel-Hady et al. reported the mean IVC diameters (IVC max + IVC min / 2) in preterm infants (mean gestational age of 30.4 ± 1.6 weeks and birth weight of 1.8 ± 0.2 kg) at the median postnatal age of 7 days ( 9 ). They found the mean IVC diameters to be 4.3 ± 0.5 mm and 3.5 ± 0.6 mm in infants during nCPAP and off nCPAP, respectively. In our study, the median values of IVC max and IVC min on the postnatal 7th day were 2.63 and 2.03 mm, respectively. The median gestational age of our study was similar to that of Abdel-Hady et al.’s study; however, the median birth weight of our infants was 1.3 kg. The smaller birth weight of our cases could explain these relatively smaller diameters of the IVC. Pawale et al. assessed hemodynamic changes in 37 preterm neonates with a mean gestational age of 30 weeks with shock. In that study, IVC size 50% were considered to represent hypovolemia. After the resolution of shock with fluid resuscitation, the median IVC CI values decreased from 42–25% ( 8 ). Also, Saini et al. studied functional echocardiographic preload markers in neonates with a mean gestational age of 30.3 weeks with septic shock, reporting the median IVC CI as 20% in their control group, which is similar to our results ( 7 ). International guidelines strongly recommend delayed cord clamping (DCC) for at least 30 seconds, as it increases ventricular preload through continued placental transfusion and improves neonatal hemodynamic stability compared to immediate cord clamping ( 39 ). This additional blood flow supports smoother hemodynamic transitions during the early phases of neonatal lung ventilation before cord clamping ( 40 ). Although DCC is widely endorsed, a limitation of our study was the inability to perform DCC in all cases, which may have contributed to the relatively smaller IVC diameters observed in our cohort. Both M-mode and B-mode tracings have been used in various studies to measure IVC diameters ( 2 , 9 , 32 , 41 ). We preferred to use M-mode imaging, which may be another limitation. Additionally, the small sample size was another limitation of our study. Hemodynamically, cardiac preload and intravascular volume status are often assessed by methods such as RUPV PV Doppler and cardiac filling by eye-balling. Most preterm infants require respiratory support during the first days of life. Since IVC indices are unaffected by respiratory support, they may be useful in routine hemodynamic assessment of preload and intravascular volume status in preterm neonates, along with other methods. Moreover, the baseline IVC indices reported in this study might be a helpful reference for neonatologists during hemodynamic investigation. In conclusion, this study reported baseline IVC parameters in preterm neonates during the first week of life. We found that IVC indices (CI, DI, and RVI) remained stable with varying levels of respiratory support. These IVC indices might be integrated into routine hemodynamic assessment to determine preload and intravascular volume status. Further studies with larger samples are needed to assess IVC parameters in preterm neonates more accurately and reliably. Declarations Finance and Support No financial support Previous presentations The study has not been presented at any congress before. Conflict of interest statement The authors report no conflict of interest Ethical Approval The Ethics Committee approved this study of the Medeniyet University School of Medicine in February 2022 with the approval number of 2022/0093 Credit Author Contributions IU: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Validation, Roles/Writing - original draft, Writing - review & editing; contributed to the analysis of data, interpretation of the data, drafting/writing of the EYI : Conceptualization, Formal analysis, Investigation, Methodology, Project administration, Writing - review & editing; contributed to the analysis of data, interpretation of the data, drafting/writing of the manuscript SHO: Conceptualization, Formal analysis, Investigation, Methodology, Project administration, Writing - review & editing; contributed to the analysis of data, interpretation of the data, drafting/writing of the manuscript FO: Conceptualization, Methodology, Project administration, review & editing; contributed to the analysis of data, interpretation of the data, and overall supervision of the study. Acknowledgments We thank Dr. Haldun Akoglu from Marmara University School of Medicine, Department of Emergency Medicine, for his assistance with statistical analysis. References Siassi B, Noori S, Wong P, Acherman R. Practical Neonatal Echocardiography. McGraw Hill Professional; 2018. 297 p. Mugloo MM, Malik S, Akhtar R. Echocardiographic Inferior Vena Cava Measurement As An Alternative to Central Venous Pressure Measurement in Neonates. Indian J Pediatr. 2017;84(10):751–6. Conlon TW, Baker D, Bhombal S. Cardiac point-of-care ultrasound: Practical integration in the pediatric and neonatal intensive care settings. Eur J Pediatr. 2024;183(4):1525–41. Singh Y. Echocardiographic Evaluation of Hemodynamics in Neonates and Children. Front Pediatr. 2017;5:201. Mayse ML. Chapter 8. Ultrasound of the Inferior Vena Cava. In: Carmody KA, Moore CL, Feller-Kopman D, editors. Handbook of Critical Care and Emergency Ultrasound [Internet]. 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Osman AA, Albalawi M, Dakshinamurti S, Hinton M, Elhawary F, Mawlana W, et al. The perfusion index histograms predict patent ductus arteriosus requiring treatment in preterm infants. Eur J Pediatr. 2021;180(6):1747–54. Jain A, EL-Khuffash AF, Van Herpen CH, Resende MHF, Giesinger RE, Weisz D, et al. Cardiac Function and Ventricular Interactions in Persistent Pulmonary Hypertension of the Newborn. Pediatr Crit Care Med. 2021;22(2):e145–57. Elsayed Y, Wahab MGA, Mohamed A, Fadel NB, Bhombal S, Yousef N, et al. Point-of-care ultrasound (POCUS) protocol for systematic assessment of the crashing neonate-expert consensus statement of the international crashing neonate working group. Eur J Pediatr. 2023;182(1):53–66. Jasani B, Martins FF, Weisz DE, Jain A, Giesinger RE, Joye S, et al. Patent ductus arteriosus shunt volume in preterm neonates using pulmonary vein diastolic velocity. Pediatr Res. 2022;91(1):4–7. Agata Y, Hiraishi S, Oguchi K, Nowatari M, Hiura K, Yashiro K, et al. Changes in pulmonary venous flow pattern during early neonatal life. Br Heart J. 1994;71(2):182–6. Hong YM, Choi JY. Pulmonary venous flow from fetal to neonatal period. Early Hum Dev. 2000;57(2):95–103. James AT, Corcoran JD, Franklin O, El-Khuffash AF. Clinical utility of right ventricular fractional area change in preterm infants. Early Hum Dev. 2016;92:19–23. Hruda J, Rothuis EGM, van Elburg RM, Sobotka-Plojhar MA, Fetter WPF. Echocardiographic assessment of preload conditions does not help at the neonatal intensive care unit. Am J Perinatol. 2003;20(6):297–303. Basu S, Sharron M, Herrera N, Mize M, Cohen J. Point-of-Care Ultrasound Assessment of the Inferior Vena Cava in Mechanically Ventilated Critically Ill Children. J Ultrasound Med Off J Am Inst Ultrasound Med. 2020;39(8):1573–9. Bilgili B, Haliloglu M, Tugtepe H, Umuroglu T. The Assessment of Intravascular Volume with Inferior Vena Cava and Internal Jugular Vein Distensibility Indexes in Children Undergoing Urologic Surgery. J Investig Surg Off J Acad Surg Res. 2018;31(6):523–8. Barbier C, Loubières Y, Schmit C, Hayon J, Ricôme JL, Jardin F, et al. Respiratory changes in inferior vena cava diameter are helpful in predicting fluid responsiveness in ventilated septic patients. Intensive Care Med. 2004;30(9):1740–6. Feissel M, Michard F, Faller JP, Teboul JL. The respiratory variation in inferior vena cava diameter as a guide to fluid therapy. Intensive Care Med [Internet]. 2004 Sep [cited 2023 Dec 4];30(9). Available from: http://link.springer.com/ 10.1007/s00134-004-2233-5 Kaptein MJ, Kaptein EM. Inferior Vena Cava Collapsibility Index: Clinical Validation and Application for Assessment of Relative Intravascular Volume. Adv Chronic Kidney Dis. 2021;28(3):218–26. Achar SK, Sagar MS, Shetty R, Kini G, Samanth J, Nayak C, et al. Respiratory variation in aortic flow peak velocity and inferior vena cava distensibility as indices of fluid responsiveness in anaesthetised and mechanically ventilated children. Indian J Anaesth. 2016;60(2):121–6. De Souza TH, Giatti MP, Nogueira RJN, Pereira RM, Soub ACS, Brandão MB. Inferior Vena Cava Ultrasound in Children: Comparing Two Common Assessment Methods*. Pediatr Crit Care Med. 2020;21(4):e186–91. Narayanaswamy V, Harohalli A V, Swamy RS, Nagesh N K. Correlation of Plethysmograph Variability Index with Inferior Vena Cava Index in Spontaneously Breathing Neonates – A Cross Sectional Study. Indian J Pediatr. 2024;91(1):81–3. Jarosz-Lesz A, Michalik K, Maruniak-Chudek I. Baseline Diameters of Inferior Vena Cava and Abdominal Aorta Measured by Ultrasonography in Healthy Term Neonates During Early Neonatal Adaptation Period. J Ultrasound Med Off J Am Inst Ultrasound Med. 2018;37(1):181–9. Levy PT, Diodena B, Holland MR, Sekarski TJ, Lee CK, Mathur A, et al. Right Ventricular Function in Preterm and Term Neonates: Reference Values for Right Ventricle Areas and Fractional Area of Change. J Am Soc Echocardiogr Off Publ Am Soc Echocardiogr. 2015;28(5):559–69. Groves AM, Kuschel CA, Knight DB, Skinner JR. Does retrograde diastolic flow in the descending aorta signify impaired systemic perfusion in preterm infants? Pediatr Res. 2008;63(1):89–94. Sloot SC, De Waal KA, Van Der Lee JH, Van Kaam AH. Central blood flow measurements in stable preterm infants after the transitional period. Arch Dis Child - Fetal Neonatal Ed. 2010;95(5):F369–72. Blehar DJ, Resop D, Chin B, Dayno M, Gaspari R. Inferior vena cava displacement during respirophasic ultrasound imaging. Crit Ultrasound J. 2012;4(1):18. 2023 American Heart Association and American Academy of Pediatrics Focused Update on Neonatal Resuscitation: An Update to the American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care [Internet]. [cited 2024 Feb 13]. Available from: https://www.ahajournals.org/doi/epub/ 10.1161/CIR.0000000000001181 Lara-Cantón I, Badurdeen S, Dekker J, Davis P, Roberts C, te Pas A, et al. Oxygen saturation and heart rate in healthy term and late preterm infants with delayed cord clamping. Pediatr Res. 2022;1–6. Horoz OO, Yildizdas D, Aslan N, Coban Y, Misirlioglu M, Haytoglu Z, et al. Sonographic measurements of Inferior Vena Cava, Aorta, anda IVC/aorta ratio in healthy children. Niger J Clin Pract. 2022;25(6):825–32. Additional Declarations There is NO conflict of interest to disclose. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: revise 21 Nov, 2024 Review # 2 received at journal 18 Nov, 2024 Review # 1 received at journal 15 Nov, 2024 Reviewer # 2 agreed at journal 08 Nov, 2024 Reviewer # 1 agreed at journal 06 Nov, 2024 Reviewers invited by journal 31 Oct, 2024 Submission checks completed at journal 29 Oct, 2024 First submitted to journal 28 Oct, 2024 Unknown event 28 Oct, 2024 Editor assigned by journal 27 Oct, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5342801","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":372624008,"identity":"78463dbc-ac28-4eb6-88be-6b9963caf622","order_by":0,"name":"Irem Unal","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA7UlEQVRIiWNgGAWjYDCCA4wNEAY7+/EfH4A0GzvRWph5EiRngLQwE9QCYzAzGEjzQBj4Ad/tw20fPuYczuNvZkgwtvm1TZ6PmYERKIJbi+S5xOaZM7cdLpY4zHggObfvtmEbMwOz5MxtuLUYnGFsZubddjix4TBDwuHcntuMQC1sQBECWv4Ctcw/zGDYbNlz2544LYxALRsOMxgzM/y4nUhQiyRQC2PvtvTEjYd50hh7G24ntzEzNuP1C98Z9scMP7dZJ8473n6M4cef27bz25sPfviIRwsqYGwDkw3EqgeBP6QoHgWjYBSMgpECAP0pU9Fjf1o0AAAAAElFTkSuQmCC","orcid":"","institution":"Istanbul Sancaktepe Sehit Prof. Dr. Ilhan Varank Training and Research Hospital,","correspondingAuthor":true,"prefix":"","firstName":"Irem","middleName":"","lastName":"Unal","suffix":""},{"id":372624009,"identity":"f71c45e5-6fde-41ae-8584-ede8cbec9222","order_by":1,"name":"Ebru Yalin Imamoglu","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Ebru","middleName":"Yalin","lastName":"Imamoglu","suffix":""},{"id":372624010,"identity":"9239fcee-beac-4f7d-a846-9128dbe4979b","order_by":2,"name":"Sibel Hatice Ozumut","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Sibel","middleName":"Hatice","lastName":"Ozumut","suffix":""},{"id":372624011,"identity":"361807e1-3d04-4c11-bee7-15281c93f698","order_by":3,"name":"Fahri Ovali","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Fahri","middleName":"","lastName":"Ovali","suffix":""}],"badges":[],"createdAt":"2024-10-27 21:00:25","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5342801/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5342801/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":69447811,"identity":"58457eaa-d326-4207-be16-117def4e8ba3","added_by":"auto","created_at":"2024-11-20 12:14:22","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":92205,"visible":true,"origin":"","legend":"\u003cp\u003eLongitudinal view of the inferior vena cava in M-mode. Asterisk (*) indicates the hepatic vein confluence with the IVC.\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5342801/v1/d4e7f27b9eb9e24275204d8f.jpg"},{"id":69446482,"identity":"61105758-f5e3-41f7-892a-3dcfb40ce361","added_by":"auto","created_at":"2024-11-20 12:06:22","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":74213,"visible":true,"origin":"","legend":"\u003cp\u003eLongitudinal view of the abdominal aorta in B-mode.\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5342801/v1/68ed1117972764249f95510b.jpg"},{"id":69448209,"identity":"688d70cf-76cc-4e2e-9079-f543b890d527","added_by":"auto","created_at":"2024-11-20 12:22:22","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":841095,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5342801/v1/df55b9f3-8d55-4186-8f18-6ffb6eb5b49a.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e conflict of interest to disclose.","formattedTitle":"Integration of Inferior Vena Cava Measurements into Routine Functional Echocardiography in Preterm Neonates: Are We There Yet?","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eFunctional echocardiography has become crucial for assessing cardiac function and hemodynamic status in neonatal intensive care units (NICUs) (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). Among various echocardiographic parameters, inferior vena cava (IVC) measurements may provide valuable insights in the assessment of preload and intravascular volume status (\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe IVC, a structurally thin-walled and highly compliant vessel, varies in size and dynamics with changes in respiration and intravascular volume (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). This causes pulsatility during different respiratory and cardiac cycles. While these variations are primarily driven by the physiological effects of respiration, several other factors can influence IVC diameters, including intravascular volume, increased mean airway pressure, elevated pulmonary vascular resistance, heart failure, cardiac tamponade, or pneumothorax (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eEvaluation of the IVC parameters can help clinicians assess hemodynamic status and guide fluid management (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). McNamara et al. reported that IVC parameters could be used for assessing volume changes; however, these parameters are not well established in neonates, particularly those with invasive ventilation (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e). Until now, there have been a limited number of studies in the literature that integrate IVC parameters into hemodynamic assessments by functional echocardiography in neonates (\u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). The current international guidelines support the use of the IVC collapsibility index (CI) for the assessment of cardiac preload and intravascular status; however, there are no validated normative data available in the neonatal population (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). Therefore, in this study we report baseline IVC measurements and investigate the clinical factors that may affect IVC diameters, as well as the hemodynamic changes during the first week of life in preterm neonates.\u003c/p\u003e"},{"header":"METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy Design and Setting\u003c/h2\u003e \u003cp\u003eThis prospective observational study was performed in the NICU at Istanbul Medeniyet University between February 2023 and January 2024. The Institutional Review Board approved the study, and informed consent was obtained from parents before inclusion.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eParticipants\u003c/h3\u003e\n\u003cp\u003eA consecutive cohort of 30 preterm neonates who were born at \u0026lt;\u0026thinsp;34 weeks gestation, were admitted to the NICU, and survived during the first week of life were included in the study. Preterm neonates with conditions that affect intravascular status, like placental abruption, vasa previa, fetomaternal hemorrhage, and fetoplacental hemorrhage, were excluded. Cases of perinatal asphyxia, pericardial effusion, and pneumopericardium, which can cause cardiac dysfunction, and cases with pneumothorax were not included. Also, those with congenital defects, with chromosomal or other genetic abnormalities, or whose IVC could not be visualized with echocardiography were excluded from the study.\u003c/p\u003e\n\u003ch3\u003eData Collection and Follow-up\u003c/h3\u003e\n\u003cp\u003eAll preterm neonates were followed for the first week of their lives. Demographic, clinical, and maternal data, including gestational age, birth weight, gender, mode of delivery, maternal diseases, antenatal steroid administration, cord management, presence of respiratory distress syndrome or transient tachypnea of the newborn, and surfactant administration were recorded.\u003c/p\u003e \u003cp\u003ePreterm neonates were evaluated on the postnatal 1st, 3rd, and 7th days. Parameters including weight loss, total fluid intake, hemoglobin level, type of respiratory support, mean airway pressure, presence of intraventricular hemorrhage, sepsis, hemodynamically significant patent ductus arteriosus (hsPDA), systemic hypotension, use of inotropes, pulmonary hypertension (PHT), and inhaled nitric oxide (iNO) treatment were noted.\u003c/p\u003e \u003cp\u003eBlood pressure was assessed by measuring systolic, diastolic, and mean arterial pressures\u003c/p\u003e \u003cp\u003eand analyzing the trends of all measurements using a noninvasively oscillometric method (HWATIME XM750; Shenzhen Hwatime Biological Medical Electronic, Shenzhen, China). Hypotension was diagnosed if at least two values were below 2 standard deviation (SD) values for the gestational and postnatal age or if there was a trend of \u0026ge;\u0026thinsp;20% decrease in blood pressure parameters for more than 30 minutes (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e).\u003c/p\u003e\n\u003ch3\u003eLung Ultrasonography\u003c/h3\u003e\n\u003cp\u003eAll patients underwent lung ultrasound (LUS) to evaluate the presence of any lung pathology (respiratory distress syndrome, transient tachypnea of the newborn, pulmonary hemorrhage, congenital pneumonia, or pneumothorax), fluid overload, or lung aeration. Surfactant treatment was performed at the discretion of the attending neonatologist, and LUS was performed independently from the surfactant treatment.\u003c/p\u003e \u003cp\u003eLung ultrasonography was performed with a Vivid S60N scanner (General Electric Medical Systems, Milwaukee, WI, USA) using an 11 L-D linear probe. Each lung was divided into three zones (upper anterior, lower anterior, and lateral) and examined with longitudinal scans. For each lung zone, a 0- to 3-point score was given (total score ranging from 0 to 18). The LUS score was assigned as follows: score 0 indicates A-pattern (defined by the presence of only A-lines); score 1, B-pattern (defined as the presence of \u0026ge;\u0026thinsp;3 well-spaced B-lines); score 2, severe B-pattern (defined as the presence of crowded and coalescent B-lines with or without consolidations limited to the subpleural space); and score 3, extended consolidations (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e). The diameters and dynamics of the IVC, a highly compliant vessel, can increase with intravascular volume overload. Therefore, with LUS, we assessed the presence of B-line burden, reflecting the degree of lung edema, which could be seen in cases of volume overload (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe A-line pattern is observed in both a normal and hyperinflated lung. In ventilated patients, hyperinflated lungs increase right atrial pressure, resulting in IVC distension (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). Since LUS has some limitations for monitoring hyperinflation due to excessive mechanical ventilation, we planned to evaluate routine chest X-ray radiographs of the patients. Lung aeration was considered adequate when the right hemidiaphragm was at the level of the 8th rib posteriorly. Patients with flattening of diaphragms and lung expansion\u0026thinsp;\u0026gt;\u0026thinsp;8th posterior ribs were diagnosed with hyperinflation (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e).\u003c/p\u003e\n\u003ch3\u003eFunctional Echocardiography\u003c/h3\u003e\n\u003cp\u003eEchocardiographic parameters were evaluated with a GE Vivid S60N scanner (Boston, MA, USA) using a 12S phased-array sector probe. To eliminate inter-observer variability, all measurements were performed by the same experienced neonatologist (I.U.). All neonates were scanned in a resting state in the supine position.\u003c/p\u003e \u003cp\u003eTo provide a comprehensive evaluation of the cardiac functions, we assessed preload, left ventricular output (LVO), right ventricular output (RVO), tricuspid annular plane systolic excursion (TAPSE), and right ventricular (RV) fractional area change (FAC). Patients were screened for PHT on the 1st, 3rd, and 7th days and for hsPDA on the 3rd and 7th days, based on criteria outlined in previously referenced sources (\u003cspan additionalcitationids=\"CR18\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the apical four-chamber view of the heart, we assessed left ventricular filling. We estimated whether there is a kissing sign by eye-balling the difference between end-systolic and end-diastolic volumes of the left ventricle (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e). Then, the right upper pulmonary vein (RUPV) was visualized along the interatrial septum in the upper part of the left atrium using color flow Doppler to assess preload. The orifice of the RUPV was imaged at the bottom of the red color Doppler flow, and the pulsed Doppler sample volume was placed into the vessel. RUPV peak systolic velocity (RPUV PV) (m/s) was measured, considering a normal range of 0.2\u0026ndash;0.5 m/s (\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e). Tricuspid annular plane systolic excursion and RV FAC were also evaluated to detect the RV function in this apical four-chamber view. Tricuspid annular plane systolic excursion was determined by placing the M-mode cursor through the lateral tricuspid annulus and measuring the extent of longitudinal annular motion during peak systole (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). We used two-dimensional images from the apical four-chamber view to calculate RV FAC. Offline analysis involved identifying the RV cavity end-diastolic area (RVEDA) and end-systolic area (RVESA) and manually tracing the cavity area. Right ventricle FAC was calculated using the following formula: [RVEDA - RVESA] / RVEDA \u0026times; 100 (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the apical five-chamber view, we evaluated LVO to determine left ventricular function. We placed the pulsed wave Doppler above the aortic valve in the apical five-chamber view for velocity time integral (VTI), and we measured the size of the aortic valve annulus at end-systole from the parasternal long-axis view. Left ventricular output was then calculated using this formula: [3.14 \u0026times; (diameter (cm) / 2)\u0026sup2; \u0026times; VTI \u0026times; HR] / weight (kg) (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the parasternal short-axis view at the level of the pulmonary valve, we evaluated the RV function by measuring RV outflow tract diameter at end-systole, and RVO VTI was obtained by tracing the pulsed wave Doppler waveform at the same level. Right ventricular output was calculated using the same formula as LVO (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eInferior Vena Cava Measurements with Echocardiography\u003c/h2\u003e \u003cp\u003eAll IVC measurements were performed in the supine position. The ultrasound probe was placed in the substernal area with the marker pointing toward the head of the neonate. The probe was tilted rightward from the midline until it captured the longitudinal view of the IVC as it merged into the right atrium. Since the probe movement off-midline might result in measurements of a false diameter smaller than the true IVC diameter, we tried to obtain a true midline image of the IVC. The M-mode cursor was placed perpendicular to the vessel. The image was frozen, and IVC diameters were measured 1 cm caudal to the junction where the hepatic vein drains into the IVC. Then, maximum and minimum diameters of the IVC (IVC\u003csub\u003emax\u003c/sub\u003e and IVC\u003csub\u003emin\u003c/sub\u003e) were obtained in millimeters using calipers (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The IVC collapsibility index (CI), distensibility index (DI), and respiratory variation index (RVI) were calculated with the following formulas:\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eCollapsibility Index = [(IVC\u003csub\u003emax\u003c/sub\u003e - IVC\u003csub\u003emin\u003c/sub\u003e) / IVC\u003csub\u003emax\u003c/sub\u003e] \u0026times; 100,\u003c/p\u003e \u003cp\u003eDistensibility Index = [(IVC\u003csub\u003emax\u003c/sub\u003e - IVC\u003csub\u003emin\u003c/sub\u003e) / IVC\u003csub\u003emin\u003c/sub\u003e] \u0026times; 100,\u003c/p\u003e \u003cp\u003eRespiratory Variation Index = [(IVC\u003csub\u003emax\u003c/sub\u003e - IVC\u003csub\u003emin\u003c/sub\u003e) / ((IVC\u003csub\u003emax\u003c/sub\u003e + IVC\u003csub\u003emin\u003c/sub\u003e) / 2)] \u0026times; 100.\u003c/p\u003e \u003cp\u003eAfter viewing the IVC, the ultrasound probe was tilted to the left from the midline in the same echo window. The diameter of the abdominal aorta was assessed at 1 cm above the celiac trunk's origin in the longitudinal plane in B-mode (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e) (Fig.\u0026nbsp;2). Then, the IVC\u003csub\u003emax\u003c/sub\u003e / abdominal aorta (IVC\u003csub\u003emax\u003c/sub\u003e/Ao) and IVC\u003csub\u003emin\u003c/sub\u003e / abdominal aorta (IVC\u003csub\u003emin\u003c/sub\u003e/Ao) ratios were calculated. All the IVC and aorta diameters were measured from the inner wall to the inner wall.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eStatistical analyses were performed using the SPSS software version 26 (SPSS Inc., Chicago, IL, USA). The variables were investigated using visual (histograms, probability plots) and analytical methods (Kolmogorov-Smirnov test, Shapiro-Wilk test) to determine whether they were normally distributed. Descriptive analyses were presented using means and SD as the normally distributed variables. Median and interquartile range (25th and 75th percentile of distribution) were used for non-normally distributed variables. Nonparametric variables were compared using the Mann-Whitney U test, and categorical variables were compared using the chi-square test or Fisher\u0026rsquo;s exact test (when chi-square test assumptions did not hold due to low expected cell counts), where appropriate. The Friedman test was conducted on ordinal or continuous variables in the case of violations of parametric test assumptions on the 1st, 3rd, and 7th days.\u003c/p\u003e \u003cp\u003eEchocardiographic measurements and IVC parameters were compared between different respiratory support levels. Since only one patient had no respiratory support on the 1st day, comparisons were made between noninvasive support and mechanical ventilation. Nonparametric variables were compared using the Mann-Whitney U test. Student\u0026rsquo;s t-test and Welch\u0026rsquo;s test were used for normally distributed variables. On the 3rd and 7th day, nonparametric variables were compared with the Kruskal-Wallis test. One-way ANOVA and Welch\u0026rsquo;s ANOVA test were used for normally distributed variables. Bonferroni correction was applied to all values.\u003c/p\u003e \u003cp\u003eStatistically significant and nonsignificant values were reported with their corresponding 95% confidence interval values. A p-value of less than 0.05 was considered to show a statistically significant result.\u003c/p\u003e \u003cp\u003eIntra-observer variability was assessed in a randomly selected sample of 20 neonates. The same investigator, blinded to the initial results, repeated the measurements. The coefficient of variation was calculated to quantify the intra-observer variability.\u003c/p\u003e \u003c/div\u003e"},{"header":"RESULTS","content":"\u003cp\u003eDemographic characteristics of the study group are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The clinical parameters on the postnatal 1st, 3rd, and 7th days are presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e summarizes echocardiographic measurements and IVC parameters on the postnatal 1st, 3rd, and 7th days. There was a statistically significant increase in the median values of LVO, RVO, and TAPSE during the first postnatal week. Other echocardiographic parameters, including median RUPV PV and FAC values, were similar during the first postnatal week. When IVC parameters were examined, median IVC\u003csub\u003emax\u003c/sub\u003e, IVC CI, IVC DI, and IVC RVI values were found to be ​​higher on the 3rd day and at their lowest level on the 7th day. However, median IVC\u003csub\u003emax\u003c/sub\u003e/Ao values ​​were at their lowest levels on the 1st day, higher on the 3rd day, and then lower again. The other IVC parameters did not change significantly throughout the first week. The time required to perform a bedside evaluation of the IVC was approximately 1\u0026ndash;2 minutes. The intra-observer error was minimal (2%), and no significant difference was observed between the consecutive measurements.\u003c/p\u003e \u003cp\u003e\u003cstrong\u003eTable 1.\u003c/strong\u003e Demographic data of the study group\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"440\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 55.4545%;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44.5455%;\"\u003e\n \u003cp\u003e\u0026nbsp;n:30\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 55.4545%;\"\u003e\n \u003cp\u003eGestational age, median (IQR)\u003c/p\u003e\n \u003cp\u003eGestational age, n (%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; 23-27 wk\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; 28-31 wk\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; 32-34 wk\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44.5455%;\"\u003e\n \u003cp\u003e\u0026nbsp;30 [29-32]\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;9 (30)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;17 (56.7)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;4 (13.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 55.4545%;\"\u003e\n \u003cp\u003eBirth Weight, g, median (IQR)\u003c/p\u003e\n \u003cp\u003eBirth Weight, n (%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026lt;1000 g\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; 1000-1499 g\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; 1500-2499 g\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026gt;2500 g\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44.5455%;\"\u003e\n \u003cp\u003e\u0026nbsp;1347 [974-1587]\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;10 (33.3)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;11 (36.7)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;8 (26.7)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;1 (3.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 55.4545%;\"\u003e\n \u003cp\u003eFemale, n (%)\u003c/p\u003e\n \u003cp\u003eMale, n (%)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44.5455%;\"\u003e\n \u003cp\u003e\u0026nbsp;12 (40)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;18 (60)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 55.4545%;\"\u003e\n \u003cp\u003eC-section, n (%)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44.5455%;\"\u003e\n \u003cp\u003e\u0026nbsp;24 (80)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 55.4545%;\"\u003e\n \u003cp\u003eAntenatal Steroids, n (%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; None\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; Half dose\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; Full dose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44.5455%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;1 (3.3)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;8 (26.7)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;21 (70)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 55.4545%;\"\u003e\n \u003cp\u003eMaternal Diseases, n (%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; None\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; PPROM\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; GDM\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; Preeclampsia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44.5455%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e17 (56.7)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;7 (23.3)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;3 (10)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;3 (10)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 55.4545%;\"\u003e\n \u003cp\u003eCord clamping method, n (%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; ICC\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; DCC\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; Milking\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; ICR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44.5455%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;26 (86.7)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;1 (3.3)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;1 (3.3)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;2 (6.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 55.4545%;\"\u003e\n \u003cp\u003eRDS, n (%)\u003c/p\u003e\n \u003cp\u003eTTN, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44.5455%;\"\u003e\n \u003cp\u003e\u0026nbsp;18 (60)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;12 (40)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 55.4545%;\"\u003e\n \u003cp\u003eSurfactant treatment, n (%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; none\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; single dose\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; two doses\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; three doses\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44.5455%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;12 (40)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;13 (43.3)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;4 (13.3)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;1 (3.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 100%;\"\u003e\n \u003cp\u003eIQR: interquartile range, PPROM: preterm premature rupture of membranes, GDM: gestational diabetes mellitus, ICC: immediate cord clamping, DCC: delayed cord clamping, ICR: intact cord resuscitation, RDS: respiratory distress syndrome, TTN: transient tachypnea of the newborn.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of clinical parameters on the 1st, 3rd, and 7th postnatal days\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1st Day\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3rd Day\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7th Day\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWeight Change (%), median [IQR]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0 [-4.95, 0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-8.1 [-12.2, -1]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-4.24 [-10.53, 2.18]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal Fluid Intake (ml/kg/day), median [IQR]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e70 [70\u0026ndash;80]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e120 [120\u0026ndash;140]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e150 [140\u0026ndash;160]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHb, median [IQR]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e17.9 [15.9\u0026ndash;19.5]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e16.2 [14.7\u0026ndash;19.4]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e15.8 [14-17.3]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMAP, median [IQR]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.8 [7-10.5]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7 [6-8.5]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6.5 [0-9.5]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.024*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIVH, n (%)\u003c/p\u003e \u003cp\u003eStage 1\u003c/p\u003e \u003cp\u003eStage 2\u003c/p\u003e \u003cp\u003eStage 3\u003c/p\u003e \u003cp\u003ePVHI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2 (6.7)\u003c/p\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003cp\u003e2 (6.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5 (16.7)\u003c/p\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003cp\u003e1 (3.3)\u003c/p\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003cp\u003e4 (13.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7 (23.3)\u003c/p\u003e \u003cp\u003e1 (3.3)\u003c/p\u003e \u003cp\u003e2 (6.7)\u003c/p\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003cp\u003e4 (13.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ehsPDA, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5 (16.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4 (13.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.484\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSepsis, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4 (13.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9 (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11 (36.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.109\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHypotension, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1 (3.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (6.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1 (3.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.771\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLUS score (B-line burden),\u003c/p\u003e \u003cp\u003emedian (IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 [2.2-6]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 [2-6.7]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3 [0.2-6]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.037*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003eIQR: interquartile range, nCPAP: nasal continuous positive airway pressure, NIPPV: noninvasive positive pressure ventilation, SIPPV: synchronized intermittent positive pressure ventilation, HFOV: high-frequency oscillatory ventilation, MAP: mean airway pressure, IVH: intraventricular hemorrhage, PVHI: periventricular hemorrhagic infarct, hsPDA: hemodynamically significant patent ductus arteriosus, PHT: pulmonary hypertension, LUS: lung ultrasound score.\u003c/p\u003e \u003cp\u003eP values marked with asterisk (*) were calculated with the Friedman test. Other p values were calculated with the chi-square test. Statistically significant p values were marked as bold.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChanges in echocardiographic measurements and inferior vena cava parameters on the postnatal 1st, 3rd, and 7th days\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable, median (IQR)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1st Day\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3rd Day\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7th Day\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eEchocardiographic Measurements\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRUPV PV (m/sec)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.35 [0.31\u0026ndash;0.43]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.40 [0.35\u0026ndash;0.47]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.41 [0.33\u0026ndash;0.44]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.335\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLVO (ml/kg/min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e174 [136\u0026ndash;206]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e196 [162\u0026ndash;263]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e210 [188\u0026ndash;256]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRVO (ml/kg/min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e318 [237\u0026ndash;369]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e399 [354\u0026ndash;485]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e455 [344\u0026ndash;541]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTAPSE (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.60 [0.50\u0026ndash;0.70]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.70 [0.60\u0026ndash;0.87]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.80 [0.61\u0026ndash;0.90]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.026\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFAC (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e21 [15\u0026ndash;25]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26 [17\u0026ndash;30]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e27 [23\u0026ndash;30]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.233\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eIVC parameters\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIVC\u003csub\u003emax\u003c/sub\u003e (mm)\u003c/p\u003e \u003cp\u003eIVC\u003csub\u003emin\u003c/sub\u003e (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.77 [2.36\u0026ndash;3.33]\u003c/p\u003e \u003cp\u003e2.08 [1.80\u0026ndash;2.45]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.09 [2.59\u0026ndash;3.47]\u003c/p\u003e \u003cp\u003e2.33 [1.65\u0026ndash;2.60]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.63 [2.32\u0026ndash;3.27]\u003c/p\u003e \u003cp\u003e2.03 [1.74\u0026ndash;2.48]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.048\u003c/b\u003e\u003c/p\u003e \u003cp\u003e0.662\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIVC CI (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22.24 [17.39\u0026ndash;27.94]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26.20 [18.31\u0026ndash;37.65]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e21.45 [16.8\u0026ndash;28.9]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.034\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIVC DI (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e28.61 [21.06\u0026ndash;38.77]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e35.51 [22.42\u0026ndash;60.45]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e27.33 [20.21\u0026ndash;40.65]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.034\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIVC RVI (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25.02 [19.05\u0026ndash;32.48]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30.15 [20.16\u0026ndash;46.4]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e24.03 [18.34\u0026ndash;33.79]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.034\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIVC\u003csub\u003emax\u003c/sub\u003e / Ao\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.62 [0.58\u0026ndash;0.70]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.68 [0.62\u0026ndash;0.77]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.64 [0.59\u0026ndash;0.76]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.003\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIVC\u003csub\u003emin\u003c/sub\u003e / Ao\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.47 [0.40\u0026ndash;0.53]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.49 [0.40\u0026ndash;0.59]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.48 [0.40\u0026ndash;0.59]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.771\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003eRUPV PV: right upper pulmonary vein peak velocity, LVO: left ventricular output, RVO: right ventricular output, TAPSE: tricuspid annular plane systolic excursion, FAC: fractional area change, IVC\u003csub\u003emax\u003c/sub\u003e: maximum diameter of inferior vena cava, IVC\u003csub\u003emin\u003c/sub\u003e: minimum diameter of inferior vena cava, IVC CI: inferior vena cava collapsibility index, IVC DI: inferior vena cava distensibility index, IVC RVI: inferior vena cava respiratory variation index, IVC\u003csub\u003emax\u003c/sub\u003e / Ao: ratio of maximum diameter of the inferior vena cava to abdominal aorta, IVC\u003csub\u003emin\u003c/sub\u003e / Ao: ratio of minimum diameter of inferior vena cava to abdominal aorta. P values were calculated using the Friedman test. Statistically significant p values were marked as bold.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eDuring the first week, we compared echocardiographic measurements and IVC parameters in different types of respiratory support (spontaneous breathing, noninvasive, and invasive mechanical ventilation [MV]). On the 1st postnatal day, echocardiographic and IVC parameters were similar in different types of respiratory support. On the 3rd postnatal day, an increase in the median values of IVC\u003csub\u003emax\u003c/sub\u003e and IVC\u003csub\u003emax\u003c/sub\u003e /Ao was observed as respiratory support was escalated (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Post hoc analyses revealed a significant increase in IVC\u003csub\u003emax\u003c/sub\u003e between the noninvasive and MV groups (p\u0026thinsp;=\u0026thinsp;0.042) and in IVC\u003csub\u003emax\u003c/sub\u003e/Ao between the spontaneous and MV groups (p\u0026thinsp;=\u0026thinsp;0.036). On the 7th postnatal day, the median values of IVC\u003csub\u003emin\u003c/sub\u003e, IVC\u003csub\u003emax\u003c/sub\u003e/Ao, and IVC\u003csub\u003emin\u003c/sub\u003e/Ao were found to increase with higher levels of respiratory support. Post hoc analysis revealed a significant difference in the median values of IVC\u003csub\u003emin\u003c/sub\u003e, IVC\u003csub\u003emax\u003c/sub\u003e/Ao, and IVC\u003csub\u003emin\u003c/sub\u003e/Ao between the spontaneous and MV groups (p\u0026thinsp;=\u0026thinsp;0.036, p\u0026thinsp;=\u0026thinsp;0.024, and p\u0026thinsp;=\u0026thinsp;0.042, respectively). However, the median values of IVC CI, DI, and RVI did not change during the first week in different respiratory support levels.\u003c/p\u003e \u003cp\u003e\u003cstrong\u003eTable 4.\u0026nbsp;\u003c/strong\u003eEchocardiographic measurements and IVC parameters in different ventilation modes\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eSpontaneous Breathing\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003eNoninvasive Respiratory Support\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eMechanical Ventilation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003ep\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eCases, n (%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 1\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 3\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e1 (3.3)\u003c/p\u003e\n \u003cp\u003e4 (13.3)\u003c/p\u003e\n \u003cp\u003e10 (33.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e21 (70)\u003c/p\u003e\n \u003cp\u003e20 (66.6)\u003c/p\u003e\n \u003cp\u003e13 (43.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e8 (26.6)\u003c/p\u003e\n \u003cp\u003e6 (20)\u003c/p\u003e\n \u003cp\u003e7 (23.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eRUPV PV\u003csub\u003e\u0026nbsp;\u003c/sub\u003e(m/sec)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 1, median [IQR]\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 3, mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 7, mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003cp\u003e0.36 \u0026plusmn; 0.01\u003c/p\u003e\n \u003cp\u003e0.40 \u0026plusmn; 0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.38 [0.32-0.47]\u003c/p\u003e\n \u003cp\u003e0.42 \u0026plusmn; 0.1\u003c/p\u003e\n \u003cp\u003e0.43 \u0026plusmn; 0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.32 [0.29-0.35]\u003c/p\u003e\n \u003cp\u003e0.46 \u0026plusmn; 0.09\u003c/p\u003e\n \u003cp\u003e0.33 \u0026plusmn; 0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.744**\u003c/p\u003e\n \u003cp\u003e0.245\u003c/p\u003e\n \u003cp\u003e0.052\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eLVO (ml/kg/min)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 1, mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 3, mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 7, mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003cp\u003e156 \u0026plusmn; 42\u003c/p\u003e\n \u003cp\u003e199 \u0026plusmn; 53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e176 \u0026plusmn; 54\u003c/p\u003e\n \u003cp\u003e194 \u0026plusmn; 56\u003c/p\u003e\n \u003cp\u003e228 \u0026plusmn; 49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e184 \u0026plusmn; 99\u003c/p\u003e\n \u003cp\u003e369 \u0026plusmn; 108\u003c/p\u003e\n \u003cp\u003e278 \u0026plusmn; 119\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e1***\u003c/p\u003e\n \u003cp\u003e0.072\u003cstrong\u003e****\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e1****\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eRVO (ml/kg/min)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 1, mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 3, mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 7, mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003cp\u003e306 \u0026plusmn; 131\u003c/p\u003e\n \u003cp\u003e360 \u0026plusmn; 98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e317 \u0026plusmn; 124\u003c/p\u003e\n \u003cp\u003e411 \u0026plusmn; 90\u003c/p\u003e\n \u003cp\u003e494 \u0026plusmn; 134\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e282 \u0026plusmn; 76\u003c/p\u003e\n \u003cp\u003e471 \u0026plusmn; 93\u003c/p\u003e\n \u003cp\u003e479 \u0026plusmn; 183\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e1*\u003c/p\u003e\n \u003cp\u003e0.258\u003c/p\u003e\n \u003cp\u003e0.408\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eTAPSE (cm)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 1, median [IQR]\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 3, mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 7, mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003cp\u003e0.75 \u0026plusmn; 0.19\u003c/p\u003e\n \u003cp\u003e0.86 \u0026plusmn; 0.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.7 [0.6-0.7]\u003c/p\u003e\n \u003cp\u003e0.72 \u0026plusmn; 0.14\u003c/p\u003e\n \u003cp\u003e0.70 \u0026plusmn; 0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.5 [0.5-0.5]\u003c/p\u003e\n \u003cp\u003e0.70 \u0026plusmn; 0.14\u003c/p\u003e\n \u003cp\u003e0.65 \u0026plusmn; 0.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.06**\u003c/p\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003cp\u003e0.270\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eFAC (%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 1, mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 3, mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Day 7, mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003cp\u003e26 \u0026plusmn; 6\u003c/p\u003e\n \u003cp\u003e23 \u0026plusmn; 9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e20 \u0026plusmn; 6\u003c/p\u003e\n \u003cp\u003e22 \u0026plusmn; 9\u003c/p\u003e\n \u003cp\u003e28 \u0026plusmn; 9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e24 \u0026plusmn; 1\u003c/p\u003e\n \u003cp\u003e30 \u0026plusmn; 11\u003c/p\u003e\n \u003cp\u003e23 \u0026plusmn; 9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e1*\u003c/p\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eIVC\u003csub\u003emax\u0026nbsp;\u003c/sub\u003e(mm)\u003c/p\u003e\n \u003cp\u003eDay 1, mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003eDay 3, mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003eDay 7, mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003cp\u003e2.73 \u0026plusmn; 0.54\u003c/p\u003e\n \u003cp\u003e2.50 \u0026plusmn; 0.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e2.93 \u0026plusmn; 0.61\u003c/p\u003e\n \u003cp\u003e2.95 \u0026plusmn; 0.46\u003c/p\u003e\n \u003cp\u003e2.72 \u0026plusmn; 0.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e2.66 \u0026plusmn; 0.70\u003c/p\u003e\n \u003cp\u003e3.77 \u0026plusmn; 0.75\u003c/p\u003e\n \u003cp\u003e3.21 \u0026plusmn; 0.61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e1*\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e0.030\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e0.144\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eIVC\u003csub\u003emin\u003c/sub\u003e (mm)\u003c/p\u003e\n \u003cp\u003eDay 1, mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003eDay 3, mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003eDay 7, mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003cp\u003e2.13 \u0026plusmn; 0.65\u003c/p\u003e\n \u003cp\u003e1.83 \u0026plusmn; 0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e2.23 \u0026plusmn; 0.58\u003c/p\u003e\n \u003cp\u003e2.14 \u0026plusmn; 0.56\u003c/p\u003e\n \u003cp\u003e2.11 \u0026plusmn; 0.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e2.18 \u0026plusmn; 0.72\u003c/p\u003e\n \u003cp\u003e2.45 \u0026plusmn; 0.68\u003c/p\u003e\n \u003cp\u003e2.60 \u0026plusmn; 0.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e1*\u003c/p\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e0.036\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eIVC CI (%)\u003c/p\u003e\n \u003cp\u003eDay 1, mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003eDay 3, mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003eDay 7, mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003cp\u003e22.76 \u0026plusmn; 11.95\u003c/p\u003e\n \u003cp\u003e25.34 \u0026plusmn; 9.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e24.16 \u0026plusmn; 8.95\u003c/p\u003e\n \u003cp\u003e28.02 \u0026plusmn; 12.95\u003c/p\u003e\n \u003cp\u003e29.31 \u0026plusmn; 13.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e19.01 \u0026plusmn; 6.51\u003c/p\u003e\n \u003cp\u003e34.47 \u0026plusmn; 14.21\u003c/p\u003e\n \u003cp\u003e18.59 \u0026plusmn; 12.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.91*\u003c/p\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eIVC DI (%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Day 1, \u0026nbsp;mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Day 3, \u0026nbsp;mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Day 7, \u0026nbsp;mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003cp\u003e31.92 \u0026plusmn; 22.11\u003c/p\u003e\n \u003cp\u003e36.51 \u0026plusmn; 17.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e33.76 \u0026plusmn; 17.12\u003c/p\u003e\n \u003cp\u003e44.42 \u0026plusmn; 33.38\u003c/p\u003e\n \u003cp\u003e30.85 \u0026plusmn; 14.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e24.17 \u0026plusmn; 9.83\u003c/p\u003e\n \u003cp\u003e60.02 \u0026plusmn; 41.53\u003c/p\u003e\n \u003cp\u003e24.85 \u0026plusmn; 16.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.894**\u003c/p\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eIVC RVI (%)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Day 1, \u0026nbsp;mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Day 3, \u0026nbsp;mean\u0026plusmn;SD\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Day 7, \u0026nbsp;mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003cp\u003e26.43 \u0026plusmn; 15.39\u003c/p\u003e\n \u003cp\u003e30.10 \u0026plusmn; 11.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e28.05 \u0026plusmn; 11.94\u003c/p\u003e\n \u003cp\u003e33.93 \u0026plusmn; 18.92\u003c/p\u003e\n \u003cp\u003e26.11 \u0026plusmn; 10.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e21.26 \u0026plusmn; 7.89\u003c/p\u003e\n \u003cp\u003e43.23 \u0026plusmn; 22.15\u003c/p\u003e\n \u003cp\u003e21.33 \u0026plusmn; 12.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.900**\u003c/p\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eIVC\u003csub\u003emax\u0026nbsp;\u003c/sub\u003e/ Ao\u003c/p\u003e\n \u003cp\u003eDay 1, mean \u0026plusmn; SD\u003c/p\u003e\n \u003cp\u003eDay 3, mean \u0026plusmn; SD\u003c/p\u003e\n \u003cp\u003eDay 7, mean \u0026plusmn; SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003cp\u003e0.62 \u0026plusmn; 0.12\u003c/p\u003e\n \u003cp\u003e0.55 \u0026plusmn; 0.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.63 \u0026plusmn; 0.09\u003c/p\u003e\n \u003cp\u003e0.69 \u0026plusmn; 0.10\u003c/p\u003e\n \u003cp\u003e0.68 \u0026plusmn; 0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.62 \u0026plusmn; 0.13\u003c/p\u003e\n \u003cp\u003e0.85 \u0026plusmn; 0.14\u003c/p\u003e\n \u003cp\u003e0.78 \u0026plusmn; 0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e1*\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e0.042\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e0.018\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eIVC\u003csub\u003emin\u0026nbsp;\u003c/sub\u003e/ Ao\u003c/p\u003e\n \u003cp\u003eDay 1, mean \u0026plusmn; SD\u003c/p\u003e\n \u003cp\u003eDay 3, mean \u0026plusmn; SD\u003c/p\u003e\n \u003cp\u003eDay 7, mean \u0026plusmn; SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003cp\u003e0.48 \u0026plusmn; 0.15\u003c/p\u003e\n \u003cp\u003e0.40 \u0026plusmn; 0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.48 \u0026plusmn; 0.09\u003c/p\u003e\n \u003cp\u003e0.50 \u0026plusmn; 0.13\u003c/p\u003e\n \u003cp\u003e0.53 \u0026plusmn; 0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.50 \u0026plusmn; 0.11\u003c/p\u003e\n \u003cp\u003e0.55 \u0026plusmn; 0.13\u003c/p\u003e\n \u003cp\u003e0.64 \u0026plusmn; 0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 77px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e1*\u003c/p\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e0.006\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 603px;\"\u003e\n \u003cp\u003eRUPV PV: right upper pulmonary vein peak velocity, LVO: left ventricular output, RVO: right ventricular output, TAPSE: tricuspid annular plane systolic excursion, FAC: fractional area change, IVC\u003csub\u003emax\u003c/sub\u003e: maximum diameter of inferior vena cava, IVC\u003csub\u003emin:\u0026nbsp;\u003c/sub\u003eminimum diameter of inferior vena cava, IVC CI: inferior vena cava collapsibility index, IVC DI: inferior vena cava distensibility index, IVC RVI: inferior vena cava respiratory variation index, IVC\u003csub\u003emax\u0026nbsp;\u003c/sub\u003e/ Ao: ratio of maximum diameter of the inferior vena cava to abdominal aorta, IVC\u003csub\u003emin\u0026nbsp;\u003c/sub\u003e/ Ao: ratio of minimum diameter of inferior vena cava to abdominal aorta.\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eBonferroni correction was applied to all P values. P values marked with corresponding symbols were calculated with (*) \u0026nbsp;the Student t-test, \u0026nbsp;(**) the Mann-Whitney U test, (***) the Welch\u0026rsquo;s test, and (****) the Welch ANOVA. Other p values were calculated with the One-Way ANOVA test. Statistically significant p values were marked as bold.\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e \u003cp\u003eOn the 1st day, one patient had hypotension and was treated with dobutamine and adrenaline throughout the week, with terlipressin added on the 7th day. Additionally, on the 3rd day, three patients were administered dobutamine; two did not exhibit hypotension but were given inotropes based on the findings from functional echocardiography. There was no kissing sign of the left ventricle in any patient. On the 3rd postnatal day, four out of six patients receiving MV support had hsPDA. In addition, three out of these six patients received inotrope treatment. By the 7th day, no other patients were receiving inotropes, except the patient who had hypotension from the 1st day. No patients had PHT or received iNO treatment.\u003c/p\u003e \u003cp\u003eThe median LUS score reflecting B-line burden was found to be 5, 3, and 3 on the 1st, 3rd, and 7th days, respectively, which are considered low LUS scores. Volume overload was not detected in any patient. The median LUS score in patients with RDS was higher than in patients with TTN on the 1st, 3rd, and 7th days (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001 for all days). On the postnatal 3rd and 7th days, the LUS score in patients with hsPDA was statistically significantly higher than the group without hsPDA (p\u0026thinsp;=\u0026thinsp;0.006 for the 3rd day, p\u0026thinsp;=\u0026thinsp;0.013 for the 7th day). When routine chest X-rays were evaluated during the first week, there was no hyperinflation in any patient.\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eThis study provides baseline IVC diameters and hemodynamic changes in preterm neonates during the first week of life. Also, we demonstrated that the median values of IVC indices, including CI, DI, and RVI, remained stable with varying levels of respiratory support.\u003c/p\u003e \u003cp\u003eFluctuations in intrathoracic pressure during the respiratory cycle significantly affect IVC diameter. During inspiration, negative intrathoracic pressure increases, reducing right atrial pressure and increasing intra-abdominal pressure, which enhances venous return and causes IVC collapse (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). Conversely, elevated intrathoracic pressure decreases venous return during expiration, leading to IVC distension. In mechanically ventilated patients, this physiological process is reversed: increased intrathoracic pressure during mechanical inspiration raises right atrial pressure, resulting in IVC distension. Abdel-Hady et al. examined IVC diameters in 25 preterm neonates during spontaneous breathing and nasal continuous positive airway pressure (nCPAP), reporting larger IVC diameters in those receiving nCPAP (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). Similarly, in our study, IVC diameters were found to be larger in neonates requiring MV. Since the physiological variations in the IVC diameters were seen during respiratory support, the use of IVC indices, including IVC CI, DI, and RVI, is preferred in clinical practice. Specifically, IVC CI is recommended for spontaneously breathing patients, while IVC DI and RVI are more appropriate for mechanically ventilated patients (\u003cspan additionalcitationids=\"CR26 CR27 CR28 CR29\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e). To our knowledge, this is the first study to investigate IVC CI, DI, and RVI in preterm neonates, and also the first to compare IVC parameters based on the level of respiratory support. While the IVC diameters varied according to the levels of respiratory support, no significant change was observed in IVC CI, DI, and RVI. This finding suggests that these indices may be reliable markers for assessing cardiac preload and intravascular volume status in preterm infants, as has been demonstrated in adult and pediatric studies (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan additionalcitationids=\"CR26\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan additionalcitationids=\"CR32 CR33\" citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eConlon et al. reported that cardiopulmonary interactions can significantly impact IVC-based measurements (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). They also suggested that clinicians should integrate data from all cardiac views to rule out poor function and pressure overload conditions, which may contribute to visualized IVC morphology. In our study, LVO, RVO, and TAPSE showed a significant increase in the postnatal first week, while RUPV PV and FAC values increased over time but were not statistically significant. These results suggest that cardiac function improved during the first week, possibly due to postnatal adaptation and inotropic support. Our patients\u0026rsquo; median FAC values were lower than the normal term neonatal values. Studies on FAC in preterm infants have shown that FAC is correlated with gestational age, tends to be low in the first few days of life, and gradually increases over time (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e). Similarly, the RVO values in our patients were higher than the normal term neonatal values. This observation is similar to previous studies, which have shown that RVO is typically elevated in preterm infants during the early days of life (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e). Theoretically, IVC diameters could be affected by cardiac function, pulmonary vascular resistance, fluid status, and hyperinflation. Moreover, cardiac tamponade and pneumothorax may increase the IVC diameters (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). The literature lacks any IVC study that evaluates all these factors together in preterm neonates. In our study, postnatal changes in cardiac functions during the first week were consistent with gestational age, and hemodynamic parameters were within normal ranges. PHT was not present. Our patients did not have excessive weight loss or fluid overload. Also, hyperinflation was not seen in any case. Cases with cardiac tamponade and pneumothorax had already been excluded from the study.\u003c/p\u003e \u003cp\u003eSince IVC measurements are affected by respiratory movements, there is a potential for error in diameter assessment. In an adult study evaluating IVC displacement during respiro-phasic ultrasound imaging, Blehar et al. demonstrated a significantly greater movement of the IVC in the craniocaudal direction than in the mediolateral direction, which predominantly affects IVC measurements in the transverse section (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e). For this reason, we preferred to perform our measurements from the longitudinal section.\u003c/p\u003e \u003cp\u003eTo our knowledge, for the first time in the literature, Abdel-Hady et al. reported the mean IVC diameters (IVC\u003csub\u003emax\u003c/sub\u003e + IVC\u003csub\u003emin\u003c/sub\u003e / 2) in preterm infants (mean gestational age of 30.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.6 weeks and birth weight of 1.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2 kg) at the median postnatal age of 7 days (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). They found the mean IVC diameters to be 4.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5 mm and 3.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.6 mm in infants during nCPAP and off nCPAP, respectively. In our study, the median values of IVC\u003csub\u003emax\u003c/sub\u003e and IVC\u003csub\u003emin\u003c/sub\u003e on the postnatal 7th day were 2.63 and 2.03 mm, respectively. The median gestational age of our study was similar to that of Abdel-Hady et al.\u0026rsquo;s study; however, the median birth weight of our infants was 1.3 kg. The smaller birth weight of our cases could explain these relatively smaller diameters of the IVC. Pawale et al. assessed hemodynamic changes in 37 preterm neonates with a mean gestational age of 30 weeks with shock. In that study, IVC size\u0026thinsp;\u0026lt;\u0026thinsp;2.1 mm and IVC CI\u0026thinsp;\u0026gt;\u0026thinsp;50% were considered to represent hypovolemia. After the resolution of shock with fluid resuscitation, the median IVC CI values decreased from 42\u0026ndash;25% (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). Also, Saini et al. studied functional echocardiographic preload markers in neonates with a mean gestational age of 30.3 weeks with septic shock, reporting the median IVC CI as 20% in their control group, which is similar to our results (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eInternational guidelines strongly recommend delayed cord clamping (DCC) for at least 30 seconds, as it increases ventricular preload through continued placental transfusion and improves neonatal hemodynamic stability compared to immediate cord clamping (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e). This additional blood flow supports smoother hemodynamic transitions during the early phases of neonatal lung ventilation before cord clamping (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e). Although DCC is widely endorsed, a limitation of our study was the inability to perform DCC in all cases, which may have contributed to the relatively smaller IVC diameters observed in our cohort. Both M-mode and B-mode tracings have been used in various studies to measure IVC diameters (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e). We preferred to use M-mode imaging, which may be another limitation. Additionally, the small sample size was another limitation of our study.\u003c/p\u003e \u003cp\u003eHemodynamically, cardiac preload and intravascular volume status are often assessed by methods such as RUPV PV Doppler and cardiac filling by eye-balling. Most preterm infants require respiratory support during the first days of life. Since IVC indices are unaffected by respiratory support, they may be useful in routine hemodynamic assessment of preload and intravascular volume status in preterm neonates, along with other methods. Moreover, the baseline IVC indices reported in this study might be a helpful reference for neonatologists during hemodynamic investigation.\u003c/p\u003e \u003cp\u003eIn conclusion, this study reported baseline IVC parameters in preterm neonates during the first week of life. We found that IVC indices (CI, DI, and RVI) remained stable with varying levels of respiratory support. These IVC indices might be integrated into routine hemodynamic assessment to determine preload and intravascular volume status. Further studies with larger samples are needed to assess IVC parameters in preterm neonates more accurately and reliably.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFinance and Support\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo financial support\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePrevious presentations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study has not been presented at any congress before.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors report no conflict of interest\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Ethics Committee approved this study of the Medeniyet University School of Medicine in February 2022 with the approval number of 2022/0093\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCredit Author Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eIU:\u0026nbsp;\u003c/strong\u003eConceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Validation, Roles/Writing - original draft, Writing - review \u0026amp; editing; contributed to the analysis of data, interpretation of the data, drafting/writing of the\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEYI\u003c/strong\u003e: Conceptualization, Formal analysis, Investigation, Methodology, Project administration, Writing - review \u0026amp; editing; contributed to the analysis of data, interpretation of the data, drafting/writing of the manuscript\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSHO:\u0026nbsp;\u003c/strong\u003eConceptualization, Formal analysis, Investigation, Methodology, Project administration, Writing - review \u0026amp; editing; contributed to the analysis of data, interpretation of the data, drafting/writing of the manuscript\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFO:\u003c/strong\u003e Conceptualization, Methodology, Project administration, review \u0026amp; editing; contributed to the analysis of data, interpretation of the data, and overall supervision of the study.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe thank Dr. Haldun Akoglu from Marmara University School of Medicine, Department of Emergency Medicine, for his assistance with statistical analysis.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSiassi B, Noori S, Wong P, Acherman R. 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Sonographic measurements of Inferior Vena Cava, Aorta, anda IVC/aorta ratio in healthy children. Niger J Clin Pract. 2022;25(6):825\u0026ndash;32.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-perinatology","isNatureJournal":false,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"jp","sideBox":"Learn more about [Journal of Perinatology](http://www.nature.com/jp/)","snPcode":"41372","submissionUrl":"https://mts-jper.nature.com/cgi-bin/main.plex","title":"Journal of Perinatology","twitterHandle":"@jperinatology","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Inferior vena cava, echocardiography, hemodynamics, preterm neonates","lastPublishedDoi":"10.21203/rs.3.rs-5342801/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5342801/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cb\u003eObjective\u003c/b\u003e\u003c/p\u003e \u003cp\u003eTo evaluate baseline inferior vena cava measurements and investigate the clinical factors that may affect inferior vena cava diameters and hemodynamic changes during the first week of life in preterm neonates.\u003c/p\u003e\u003cp\u003e\u003cb\u003eStudy Design:\u003c/b\u003e\u003c/p\u003e \u003cp\u003eThis prospective observational study included a consecutive cohort of 30 preterm neonates born at \u0026lt;\u0026thinsp;34 weeks gestation. Echocardiographic parameters and inferior vena cava diameters were measured on the postnatal 1st, 3rd, and 7th days, and inferior vena cava indices were calculated. We then compared echocardiographic and inferior vena cava parameters in different types of respiratory support.\u003c/p\u003e\u003cp\u003e\u003cb\u003eResult\u003c/b\u003e\u003c/p\u003e \u003cp\u003eBaseline data of the inferior vena cava parameters were reported. The median values of the inferior vena cava collapsibility, distensibility, and respiratory variation indices did not change at different respiratory levels.\u003c/p\u003e\u003cp\u003e\u003cb\u003eConclusion\u003c/b\u003e\u003c/p\u003e \u003cp\u003eInferior vena cava collapsibility, distensibility, and respiratory variation indices remained stable with varying levels of respiratory support. These indices might be integrated into routine hemodynamic assessment to determine preload and intravascular volume status.\u003c/p\u003e","manuscriptTitle":"Integration of Inferior Vena Cava Measurements into Routine Functional Echocardiography in Preterm Neonates: Are We There Yet?","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-11-20 12:06:18","doi":"10.21203/rs.3.rs-5342801/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"revise","date":"2024-11-21T12:24:50+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"This content is not available.","date":"2024-11-19T04:50:11+00:00","index":2,"fulltext":"This content is not available."},{"type":"editorInvitedReview","content":"This content is not available.","date":"2024-11-15T23:01:07+00:00","index":1,"fulltext":"This content is not available."},{"type":"reviewerAgreed","content":"This content is not available.","date":"2024-11-08T11:01:42+00:00","index":2,"fulltext":"This content is not available."},{"type":"reviewerAgreed","content":"This content is not available.","date":"2024-11-06T19:03:41+00:00","index":1,"fulltext":"This content is not available."},{"type":"reviewersInvited","content":"","date":"2024-10-31T12:23:28+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-10-29T11:46:09+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Perinatology","date":"2024-10-28T18:42:08+00:00","index":"","fulltext":""},{"type":"checksFailed","content":"","date":"2024-10-28T15:08:11+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-10-27T20:58:12+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-perinatology","isNatureJournal":false,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"jp","sideBox":"Learn more about [Journal of Perinatology](http://www.nature.com/jp/)","snPcode":"41372","submissionUrl":"https://mts-jper.nature.com/cgi-bin/main.plex","title":"Journal of Perinatology","twitterHandle":"@jperinatology","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"691baf8a-3edd-4ba3-8b17-992cb3d46268","owner":[],"postedDate":"November 20th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":39663183,"name":"Health sciences/Medical research"},{"id":39663184,"name":"Health sciences/Medical research/Outcomes research"}],"tags":[],"updatedAt":"2025-03-13T14:46:24+00:00","versionOfRecord":[],"versionCreatedAt":"2024-11-20 12:06:18","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5342801","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5342801","identity":"rs-5342801","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}